The present invention relates to an apparatus for mounting a tool to a spindle of a machine such as a machine tool and the like, which is incorporated into the spindle or rotary shaft of the machine.
Generally, in a tool mounting apparatus incorporated into a spindle of a machine tool such as a machining center, a tool is mounted to the spindle in such a manner that a tool holder with the tool is inserted into the spindle, and then a pull stud of the tool holder is gripped by closing a collect attachment (which is arranged in the spindle and can be opened and closed in response to an axial movement of a pull rod) by shifting the pull rod axially by making use of resilient force of coned disc springs or a coil spring, thus fixedly attaching the tool holder with the tool to the spindle.
In the conventional tool mounting apparatus, since the coned disc springs or the coil spring were/was used to pull the pull rod for closing the collet attachment and since the inner diameter of such springs is decreased and, the other diameter of the springs is increased when the springs are compressed, it was necessary to maintain clearances between the spring and a case for accommodating the spring, and between the spring and a spring guide rod. Accordingly, during the continuous rotation of the spindle the spring might be deviated from its centered position by a distance corresponding to such clearance, which deviation or eccentricity of the spring might cause the vibration of the spindle and/or the tool being rotated, due to unbalance rotation thereof. Further, the spring itself had a limitation with respect to balance of mass during rotation thereof. Therefore, in the conventional tool mounting apparatus, there was a problem that the spindle could not be rotated effectively at a high speed due to the vibration.